Method and apparatus for controlling radiation beam intensity directed to microlithographic substrates

ABSTRACT

A method and apparatus for controlling an intensity distribution of a radiation beam directed to a microlithographic substrate. The method can include directing a radiation beam from a radiation source along the radiation path, with the radiation beam having a first distribution of intensity as the function of location in a plane generally transverse to the radiation path. The radiation beam impinges on an adaptive structure positioned in the radiation path and an intensity distribution of the radiation beam is changed from the first distribution to a second distribution by changing a state of the first portion of the adaptive structure relative to a second portion of the adaptive structure. For example, the transmissivity of the first portion, or inclination of the first portion can be changed relative to the second portion. The radiation is then directed away from the adaptive structure to impinge on the microlithographic substrate.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application relates to material disclosed in U.S.application Ser. No. ______ (attorney docket number 10829.8543US) titled“Method and Apparatus for Irradiating a Microlithographic Substrate,”filed on Aug. 30, 2001 and incorporated herein in its entirety byreference.

BACKGROUND

[0002] The present invention is directed toward methods and apparatusesfor controlling the intensity of a radiation beam directed toward amicrolithographic substrate. Microelectronic features are typicallyformed in microelectronic substrates (such as semiconductor wafers) byselectively removing material from the wafer and filling in theresulting openings with insulative, semiconductive, or conductivematerials. One typical process includes depositing a layer ofradiation-sensitive photoresist material on the wafer, then positioninga patterned mask or reticle over the photoresist layer, and thenexposing the masked photoresist layer to a selected radiation. The waferis then exposed to a developer, such as an aqueous base or a solvent. Inone case, the photoresist layer is initially generally soluble in thedeveloper, and the portions of the photoresist layer exposed to theradiation through patterned openings in the mask change from beinggenerally soluble to become generally resistant to the developer (e.g.,so as to have low solubility). Alternatively, the photoresist layer canbe initially generally insoluble in the developer, and the portions ofthe photoresist layer exposed to the radiation through the openings inthe mask become more soluble. In either case, the portions of thephotoresist layer that are resistant to the developer remain on thewafer, and the rest of the photoresist layer is removed by the developerto expose the wafer material below.

[0003] The wafer is then subjected to etching or metal dispositionprocesses. In an etching process, the etchant removes exposed material,but not material protected beneath the remaining portions of thephotoresist layer. Accordingly, the etchant creates a pattern ofopenings (such as grooves, channels, or holes) in the wafer material orin materials deposited on the wafer. These openings can be filled withinsulative, conductive, or semiconductive materials to build layers ofmicroelectronic features on the wafer. The wafer is then singulated toform individual chips, which can be incorporated into a wide variety ofelectronic products, such as computers and other consumer or industrialelectronic devices.

[0004] As the size of the microelectronic features formed in the waferdecreases (for example, to reduce the size of the chips placed inelectronic devices), the size of the features formed in the photoresistlayer must also decrease. In some processes, the dimensions (referred toas critical dimensions) of selected features are evaluated as adiagnostic measure to determine whether the dimensions of other featurescomply with manufacturing specifications. Critical dimensions areaccordingly selected to be the most likely to suffer from errorsresulting from any of a number of aspects of the foregoing process. Sucherrors can include errors generated by the radiation source and/or theoptics between the radiation source and the mask. The errors can also begenerated by the mask, by differences between masks, and/or by errors inthe etch process. The critical dimensions can also be affected by errorsin processes occurring prior to or during the exposure/developmentprocess, and/or subsequent to the etching process, such as variations indeposition processes, and/or variations in material removal processes,such as chemical-mechanical planarization processes.

[0005] One general approach to correcting lens aberrations in waferoptic systems (disclosed in U.S. Pat. No. 5,142,132 to McDonald et al.)is to reflect the incident radiation from a deformable mirror, which canbe adjusted to correct for the aberrations in the lens optics. However,correcting lens aberrations will not generally be adequate to addressthe additional factors (described above) that can adversely affectcritical dimensions. Accordingly, another approach to addressing some ofthe foregoing variations and errors is to interpose a gradient filterbetween the radiation source and the mask to spatially adjust theintensity of the radiation striking the wafer. Alternatively, a thinfilm or pellicle can be disposed over the mask to alter the intensity oflight transmitted through the mask. In either case, the filter and/orthe pellicle can account for variations between masks by decreasing theradiation intensity incident on one portion of the mask relative to theradiation intensity incident on another.

[0006] One drawback with the foregoing arrangement is that it may bedifficult and/or time-consuming to change the gradient filter and/or thepellicle when the mask is changed. A further drawback is that thegradient filter and the pellicle cannot account for new errors and/orchanges in the errors introduced into the system as the system ages orotherwise changes.

SUMMARY

[0007] The present invention is directed to methods and apparatuses forcontrolling the intensity distribution of radiation directed tomicrolithographic substrates. In one aspect of the invention, the methodcan include directing a radiation beam from a radiation source alongradiation path, with the radiation beam having a first distribution ofintensity as a function of location in a plane generally transverse tothe radiation path. The method can further include impinging theradiation beam on an adaptive structure positioned in the radiationpath, and changing an intensity distribution of the radiation beam fromthe first distribution to a second distribution different than the firstdistribution by changing a state of a first portion of the adaptivestructure relative to a second portion of the adaptive structure. Themethod can further include directing the radiation beam away from theadaptive structure along the radiation path and impinging the radiationbeam directed away from the adaptive structure on the microlithographicsubstrate.

[0008] In a further aspect of the invention, the method can includeimpinging a first portion of the radiation beam on a first portion of areflective medium and impinging a second portion of the radiation beamon a second portion of the reflective medium. The method can furtherinclude moving the first portion of the reflective medium relative tothe second portion, and reflecting at least part of the first portion ofthe radiation beam toward a first portion of a grating having a firsttransmissivity, and reflecting at least part of the second portion ofthe radiation beam toward a second portion of the grating having asecond transmissivity greater than the first transmissivity. At leastpart of the second portion of the radiation beam then passes through thegrating to impinge on the microlithographic substrate, while at leastpart of the first portion of the radiation beam is attenuated or blockedfrom passing through the grating.

[0009] The invention is also directed toward an apparatus forcontrolling an intensity distribution of radiation directed to amicrolithographic substrate. The apparatus can include a substratesupport having a support surface positioned to carry a microlithographicsubstrate, and a source of radiation positioned to direct a radiationbeam along a radiation path toward the substrate support. The apparatuscan further include an adaptive structure positioned in the radiationpath and configured to receive the radiation beam with a first intensitydistribution and transmit the radiation beam with a second intensitydistribution different than the first intensity distribution. Theadaptive structure can have a first portion and a second portion, eachpositioned to receive the radiation and changeable from a first state toa second state, wherein the adaptive structure is configured to transmitthe radiation with the second intensity distribution when the firstportion is in the first state and the second portion is in the secondstate. The apparatus can further include a controller operativelycoupled to the adaptive structure to direct at least one of the firstand second portions to change from the first state to the second stateto change an intensity distribution of the radiation beam from the firstintensity distribution to the second intensity distribution.

[0010] In a further aspect of the invention, the adaptive structure caninclude a selectively transmissive medium having a first portion alignedwith a first portion of the radiation beam when the radiation beam isemitted from the radiation source, and a second portion aligned with thesecond portion of the radiation beam. Each of the first and secondportions can have a transmissivity that is changeable from a firsttransmissivity to a second transmissivity different than the firsttransmissivity. Alternatively, the adaptive structure can include areflective medium having a first portion aligned with a first portion ofthe radiation beam when the radiation beam is emitted from the radiationsource, and a second portion aligned with a second portion of theradiation beam. Each of the first and second portions of the reflectivemedium can be coupled to at least one actuator to move from a firstinclination angle relative to the radiation path to a second inclinationangle relative to the radiation path, with the second inclination anglebeing different than the first inclination angle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a partially schematic view of an apparatus forirradiating microlithographic substrates in accordance with anembodiment of the invention.

[0012]FIG. 2 is a partially schematic view of a portion of an adaptivestructure that includes a reflective medium and a diffuser plate inaccordance with an embodiment of the invention.

[0013]FIG. 3 is a partially schematic view of an adaptive structure thatincludes a reflective medium and a diffuser plate in accordance withanother embodiment of the invention.

[0014]FIG. 4 is a partially schematic view of an adaptive structure thatincludes a selectively transmissive medium in accordance with yetanother embodiment of the invention.

[0015]FIG. 5 is a flow chart illustrating a method for adjustingcharacteristics of radiation directed toward a microlithographicsubstrate in accordance with an embodiment of the invention.

[0016]FIGS. 6A-6C are flow diagrams illustrating details of methods foradjusting the radiation directed toward microlithographic substrates inaccordance with further embodiments of the invention.

DETAILED DESCRIPTION

[0017] The present disclosure describes methods and apparatuses forcontrolling the intensity of radiation directed toward amicrolithographic substrate. The term “microlithographic substrate” isused throughout to include substrates upon which and/or in whichmicroelectronic circuits or components, data storage elements or layers,vias or conductive lines, micro-optic features, micromechanicalfeatures, and/or microbiological features are or can be fabricated usingmicrolithographic techniques. Many specific details of certainembodiments of the invention are set forth in the following descriptionand in FIGS. 1-6C to provide a thorough understanding of theseembodiments. One skilled in the art, however, will understand that thepresent invention may have additional embodiments, and that theinvention may be practiced without several of the details describedbelow.

[0018]FIG. 1 schematically illustrates an apparatus 110 for controllablyirradiating a microlithographic substrate 160 in accordance with anembodiment of the invention. The apparatus 110 can include a radiationsource 120 that directs an electromagnetic radiation beam 128 along aradiation path 180 toward the microlithographic substrate 160. Theapparatus 110 can further include an adaptive structure 140 that adjuststhe intensity distribution of the incoming radiation beam 128.Optionally, the radiation beam 128 can then pass through a lens system123 configured to shape and/or magnify the radiation emitted by thesource 120. Optionally, the apparatus 110 can further include adiffractive element 122 to diffuse the radiation, and a light tube 124positioned to generate a plurality of images of the radiation source120. The light tube 124 and/or or a sizing lens 125 can size theradiation beam 128, which can then be directed by a mirror 126 through afocusing lens 127 to a reticle or mask 130 along a reticle radiationpath segment 181 a.

[0019] The reticle 130 can include reticle apertures 131 through whichthe radiation passes to form an image on the microlithographic substrate160. The radiation passes through a reduction lens 139 which reduces theimage pattern defined by the reticle to a size corresponding to the sizeof the features to be formed on the microlithographic substrate 160. Theradiation beam 128 then travels in a second direction 182 along asubstrate radiation path segment 182 a, and impinges on aradiation-sensitive material (such as a photoresist layer 161) of themicrolithographic substrate 160 to form an image on the layer 161. Inone embodiment, the beam 128 impinging on the layer 161 can have agenerally rectangular shape with a width of from about 5 mm. to about 8mm. and a length of about 26 mm. In other embodiments, the beam 128incident on the layer 161 can have other shapes and sizes. In oneembodiment, the radiation can have a wavelength in the range of about157 nanometers or less (for example, 13 nanometers) to a value of about365 nanometers or more. For example, the radiation can have a wavelengthof about 193 nanometers. In other embodiments, the radiation can haveother wavelengths suitable for exposing the layer 161 on themicrolithographic substrate 160.

[0020] The microlithographic substrate 160 is supported on a substratesupport 150. In one embodiment (a scanner arrangement), the substratesupport 150 moves along a substrate support path 151, and the reticle130 moves in the opposite direction along a reticle path 132 to scan theimage produced by the reticle 130 across the layer 161 while theposition of the radiation beam 128 remains fixed. Accordingly, thesubstrate support 150 can be coupled to a support actuator 154 and thereticle 130 can be coupled to a reticle actuator 137.

[0021] As the reticle 130 moves opposite the microlithographic substrate160, the radiation source 120 can flash to irradiate successive portionsof the microlithographic substrate 160 with corresponding successiveimages produced by the reticle 130, until an entire field of themicrolithographic substrate 160 is scanned. In one embodiment, theradiation source 120 can flash at a rate of about 20 cycles during thetime required for the microlithographic substrate 160 to move by onebeam width (e.g., by from about 5 mm. to about 8 mm.). In otherembodiments, the radiation source 120 can flash at other rates. In anyof these embodiments, the radiation source 120 can flash at the samerate throughout the scanning process (assuming the reticle 130 and thesubstrate 150 each move at a constant rate) to uniformly irradiate eachfield. Alternatively, the radiation source 120 can deliver a continuousradiation beam 128. In either embodiment, each field can include one ormore dice or chips, and in other embodiments, each field can includeother features.

[0022] In another embodiment (a stepper arrangement), the radiation beam128 and the reticle 130 can expose an entire field of themicrolithographic substrate 160 in one or more flashes, while thereticle 130 and the substrate support 150 remain in a fixed transverseposition relative to the radiation path 180. After the field has beenexposed, the reticle 130 and/or substrate support 150 can be movedtransverse to the radiation path 180 to align other fields with theradiation beam 128. This process can be repeated until each of thefields of the microlithographic substrate 160 is exposed to theradiation beam 128. Suitable scanner and stepper devices are availablefrom ASML of Veldhoven, The Netherlands; Canon USA, Inc., of LakeSuccess, N.Y.; and Nikon, Inc. of Tokyo, Japan.

[0023] In a further aspect of this embodiment, a controller 170 isoperatively coupled to the reticle 130 (or the reticle actuator 137) andthe substrate support 150 (or the support actuator 154). Accordingly,the controller 170 can include a processor, microprocessor or otherdevice that can automatically (with or without user input) control andcoordinate the relative movement between these elements. The controller170 can also be coupled to the adaptive structure 140 to control theintensity distribution of the radiation beam 128, as described ingreater detail below.

[0024]FIG. 2 is a schematic view of the adaptive structure 140 describedabove with reference to FIG. 1 in accordance with an embodiment of theinvention. In one aspect of this embodiment, the adaptive structure 140can include a reflective medium 141, a grating 144, and a diffuser 148,all positioned along the radiation path 180. The reflective medium 141can include a two-dimensional array of movable reflective elements 142(four of which are shown schematically in FIG. 2 as elements 142 a-d),coupled to a corresponding plurality of actuators 143 (shown asactuators 143 a-d). For example, the reflective medium 141 can include adigital multi-mirror device, such as a device available from TexasInstruments of Dallas, Tex. Accordingly, each reflective element 142 canform a portion of a larger reflective surface 149 and can moveindependently of the other reflective elements. The interstices betweenthe reflective elements 146 can be filled with a reflective (oroptionally, a non-reflective) material that allows for relative movementof adjacent elements 142.

[0025] The reflective elements 142 direct the radiation beam 128 to thegrating 144. In one embodiment, the grating 144 can include firstportions or regions 145 (shown as first regions 145-a-d) positionedbetween second portions or regions 146 (shown as second regions 146a-d). In one embodiment, the first regions 145 can be opaque and thesecond regions 146 can be transparent. In other embodiments, the firstand second regions 145, 146 can have other transmissivities for which afirst transmissivity of the first regions 145 is less than a secondtransmissivity of the second regions 146. In one embodiment, the firstregions 145 can be formed by a rectilinear grid of lines disposed on anotherwise transparent (or at least more transmissive) substrate, such asquartz. In other embodiments, the first regions 145 can have othershapes and arrangements. In any of these embodiments, the first regions145 can intersect some of the radiation directed by the reflectivemedium 141 toward the grating 144 to locally reduce the intensity of theradiation passing through the grating 144. In a further aspect of thisembodiment, the first regions 145 can have an absorptive coating 147facing toward the reflective medium 141 to prevent the intersectedradiation from reflecting back toward the reflective medium 141.

[0026] The diffuser 148 receives the radiation passing through thegrating 144 and smoothes what might otherwise be discrete shadows ordiscontinuities in the intensity distribution produced by the firstregions 145 of the grating 144. Accordingly, the diffuser 148 canproduce an intensity distribution represented schematically in FIG. 2 byline 182 and described in greater detail below.

[0027] In operation, each of the reflective elements 142 of thereflective medium 141 can be positioned to direct portions of theimpinging radiation beam 128 (which has an initial, generally uniformintensity distribution across the section of the beam) in a selectedmanner to produce a different intensity distribution. For example,element 142 b can be positioned to direct a radiation beamlet 128 bdirectly between two first regions 145 b and 145 c to produce anundeflected level of intensity, as indicated by line 182. Elements 142 cand 142 d can be positioned to direct radiation beamlets 128 c and 128d, respectively, directly toward first region 145 d. Accordingly, theradiation reflected by these elements will have a reduced intensity, asis also shown by line 182. The reflective element 142 a can bepositioned to direct a radiation beamlet 128 a that illuminates lessthan the entire corresponding first region 145 a to produce a level ofintensity that is less than that produced by element 142 b, but greaterthan that produced by elements 142 c and 142 d. Similar adjustments canbe made to the entire array of reflective elements 142 to selectivelytailor the intensity distribution to a selected level.

[0028] In one embodiment, the resolution of the changes in intensitydistribution shown in FIG. 2 can be relatively coarse in comparison tothe individual features produced on the microlithographic substrate 160(FIG. 1). For example, the microelectronic or other microlithographicfeatures formed in the microlithographic substrate 160 can havedimensions on the order of less than one micron, while the distancebetween adjacent portions of the radiation beam 128 having differentintensities can be from about 0.3 mm. to about 1 mm. or greater. In oneembodiment, the shift in intensity can be less than about 10% of theundeflected intensity of the radiation beam 128 (e.g., less than about10% of the intensity incident on the reflective medium 141). In otherembodiments, the maximum deviation in intensity from any portion of theradiation beam 128 to any other portion can be less than about 5% of theincident intensity, and in a specific embodiment, can be from about 1%to about 2% of the incident intensity. Accordingly, the grating 144 canhave an open area of about 90 percent in one embodiment, and can have agreater open area in other embodiments.

[0029]FIG. 3 is a partially schematic illustration of another embodimentof the adaptive structure 140 described above with reference to FIG. 2.In one aspect of this embodiment, the adaptive structure 140 does notinclude a grating 144. Accordingly, the reflective elements 142 a-d candirect corresponding radiation beamlets 128 a-d at different anglesdirectly to the diffuser 148. The diffuser 148 can smooth outtransitions between regions of the radiation beam 128 having differentintensities (generally as described above) to produce a radiationdistribution line 382. In one aspect of this embodiment, the radiationbeamlets 128 c and 128 d can combine to produce a local intensitygreater than the undeflected intensity. One advantage of the arrangementshown in FIG. 3 when compared to the arrangement shown in FIG. 2 is thatthe overall intensity of the radiation beam shown in FIG. 3 can begreater than that shown in FIG. 2 because the grating 144 (which canabsorb a portion of the radiation) is eliminated. Conversely, anadvantage of the arrangement shown in FIG. 2 is that the grating 144 canprovide an added degree of control over the reflected radiation beam 128(for example, it may dampen the effect of system vibrations), whencompared to an arrangement that includes the diffuser 148 alone.

[0030]FIG. 4 is a partially schematic illustration of an adaptivestructure 440 having a mirror 483 that directs the radiation beam 128 toimpinge on a variably transmissive medium 480. The variably transmissivemedium 480 can include a liquid crystal material arranged to formvariably transmissive elements 481 (shown in FIG. 4 as elements 481a-c). The variably transmissive elements 481 can be coupled to a sourceof electrical power and can be reversibly changed from one transmissivestate to another, within a range of transmissivities that can vary fromtransparent or nearly transparent to opaque or nearly opaque. Forexample, the variably transmissive elements 481 a can be selected to betransparent or at least approximately transparent to pass a portion ofthe radiation beam 128 through the variably transmissive medium 480 at ahigh level of intensity, as shown by intensity line 482. The variablytransmissive elements 481 b can have a lower transmissivity to reducethe intensity of a corresponding portion of the radiation beam 128. Thevariably transmissive elements 481 c can have a transmissivity lowerthan that of the elements 481 b to further reduce the intensity of acorresponding portion of the radiation beam 128. In other embodiments,the states of the variably transmissive elements 481 can be changed inother manners to produce any of a wide variety of intensitydistributions in the radiation beam 128.

[0031] In other embodiments, the adaptive structure 440 can have otherarrangements. For example, the variably transmissive medium 480 caninclude materials other than a liquid crystal material. In anotheralternate embodiment, the variably transmissive medium can include asingle, continuously variable element in place of the plurality ofelements described above. In any of the foregoing embodiments, theadaptive structure 440 can adjust the intensity of the radiation beam tothe levels and resolutions described above with reference to FIG. 2.

[0032]FIG. 5 is a flow diagram illustrating steps of a method for usingany of the apparatuses described above with reference to FIGS. 1-4 inaccordance with an embodiment of the invention. FIGS. 6A-6C illustratefurther details of the steps shown in FIG. 5. Beginning with FIG. 5, amethod 500 can include irradiating a microlithographic substrate with aradiation beam having a selected intensity distribution to form an imageon the microlithographic substrate (step 502). The method can furtherinclude forming features in the microlithographic substrate based on theimage formed in step 502 (step 504). In step 506, characteristics of thefeatures formed in the microlithographic substrate are compared withtarget characteristics. In step 508, the process includes determiningwhether the characteristics of the features are within pre-selectedlimits. If the characteristics are within the limits, the process ends.If not, the configuration or setting of the adaptive structure isadjusted in step 510, and the process is repeated with a differentmicrolithographic substrate.

[0033]FIG. 6A illustrates details of an embodiment of the process forforming features in the microlithographic substrate based on the imageformed with the radiation beam (step 504). In one aspect of thisembodiment, the process can further include developing the image in aphotoresist layer (step 602). The material beneath the photoresist layercan be selectively etched to form recesses (step 604). The recesses canbe filled with a conductive, semiconductive, or non-conductive material(step 606). Once the recesses have been filled, excess material can beremoved from the microlithographic substrate, for example, bychemical-mechanical planarization, in step 608.

[0034]FIG. 6B illustrates further details of embodiments of the processfor comparing characteristics of features in the microlithographicsubstrate with target characteristics (step 506). In step 610, theprocess can include selecting the features of the microlithographicsubstrate. For example, the features can include control structuresspecifically formed in the microlithographic substrate for diagnosticpurposes. Alternatively, the process can include selecting otherstructures of the microlithographic substrate, such as featuresconfigured to be operated by the end user. In still a furtherembodiment, the features can include features formed in a photoresistlayer prior to etching or depositing materials on the microlithographicsubstrate. In any of these embodiments, the process can includecomparing measured feature dimensions with target values for the samedimensions (step 612). In a specific aspect of this process, the methodcan include analyzing the features with an electron microscope andcomparing the measured results with target results. In anotherembodiment (step 614), the method can include comparing the conductivityof one or more features with a target conductivity. In any of theforegoing embodiments, the process of comparing characteristics ofmicroelectronic or other microlithographic features with targetcharacteristics can be repeated until an entire die is checked (step616) and/or until an entire field and/or wafer is checked (step 618).The process can also be carried out on a plurality of wafers or othermicrolithographic substrates.

[0035]FIG. 6C illustrates details of an embodiment of the process ofadjusting the setting of the adaptive structure (step 510). For example,when the adaptive structure includes tiltable or otherwise moveablereflective elements, the process can include adjusting the inclinationangle of the reflective elements relative to the radiation path (step620). Alternatively, for example, when the adaptive structure includesvariably transmissive elements, the process can include adjusting thetransmissivity of selected transmissive elements (step 622). In eitherembodiment, the process can further include replacing an initialmicrolithographic substrate with a subsequent microlithographicsubstrate after the adjustment (step 624), for example, to determine theeffect of the adjustment.

[0036] One feature of the arrangements described above with reference toFIGS. 1-6C is that the adaptive structures can be easily altered byproviding instructions from the controller 170. An advantage of thisfeature is that unlike conventional filters and pellicles, the structurethat tailors the intensity of the radiation need not be removed from thesystem and replaced in order to produce a new intensity distribution.Accordingly, this arrangement can be less expensive than conventionalarrangements because it requires fewer pieces of hardware. Thearrangement can also be more efficient than conventional arrangementsbecause it can take less time to change the intensity distribution ofthe radiation beam.

[0037] Another advantage of the arrangements described above withreference to FIG. 1-6C is that they can be used to account for a widerange of factors that can systematically cause characteristics of themicroelectronic or other microlithographic features to deviate fromtheir target characteristics. For example, the adaptive structure can beadjusted to account for slight variations across a given mask and/orbetween different masks or reticles that are configured to produce thesame illumination pattern on one or more microlithographic substrates,but that may fail to do so due to manufacturing tolerances or errors.Alternatively, the adaptive structure can be used to account for thedegradation that can occur to a single mask and/or other system opticsand/or the radiation source over the course of time. Still further, theadaptive structure can tailor the intensity distribution of the incidentradiation beam to correspond to a variety of different masks having awide variety of disparate aperture patterns. For example, the adaptivestructure can have a first configuration when used with a first mask toform one type of microelectronic die or chip, and can be changed to asecond configuration when used with a second mask to form a differenttype of microelectronic die or chip.

[0038] In other embodiments, the adaptive structure can be used toaccount for variations produced by other aspects of the process orprocesses for forming microelectronic devices or other microlithographicfeatures. For example, if a particular section of the microlithographicsubstrate or microlithographic substrate field tends to etch more slowlythan another (producing features that are undersized), the intensity ofthe radiation directed to this region can be increased. The increasedradiation can locally increase the radiation dose and therefore the sizeof the features formed in that region. If one region of themicrolithographic substrate has a non-uniform optical thickness as aresult of prior material deposition and/or removal processes (such asCMP processes), this can alter the manner in which theradiation-sensitive material subsequently disposed on themicrolithographic substrate behaves. For example, optically non-uniformregions may reflect incident radiation differently than uniform regions,which can change the amount of reflected radiation absorbed by thephotoresist layer on the microlithographic substrate. The intensitydistribution of the radiation directed toward this portion of thesubstrate can be altered to account for this non-uniformity, for exampleby increasing the incident radiation intensity where the radiationabsorption is less than a target level, and/or decreasing the incidentradiation intensity where the radiation absorption is greater than atarget level.

[0039] From the foregoing, it will be appreciated that specificembodiments of the invention have been described herein for purposes ofillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the invention. For example, inone embodiment, the apparatus can include both a deformable reflectivemedium and a variably transmissive medium to increase the degree ofcontrol over the intensity of the radiation exiting the adaptivestructure. In another embodiment, any of the refractive elementsdescribed above, including the reticle, can be replaced with reflectiveelements that perform generally the same function. Accordingly, theinvention is not limited except as by the appended claims.

1-45. (Cancelled)
 46. An apparatus for controlling an intensitydistribution of radiation directed to a microlithographic substrate,comprising: a substrate support having a support surface positioned tocarry a microlithographic substrate; a source of radiation positioned todirect a radiation beam along a radiation path toward the substratesupport; an adaptive structure positioned in the radiation path andconfigured to receive the radiation beam with a first intensitydistribution and transmit the radiation beam with a second intensitydistribution different than the first intensity distribution, theadaptive structure having a first portion and a second portion, eachpositioned to receive the radiation and each changeable from a firststate to a second state, and wherein the adaptive structure isconfigured to transmit the radiation with the second intensitydistribution when the first portion is in the first state and the secondportion is in the second state; and a controller operatively coupled tothe adaptive structure to direct at least one of the first and secondportions to change from the first state to the second state to change anintensity distribution of the radiation beam from the first intensitydistribution to the second intensity distribution.
 47. The apparatus ofclaim 46 wherein the adaptive structure includes a selectivelytransmissive medium having a first portion aligned with a first portionof the radiation beam when the radiation beam is emitted from theradiation source, and a second portion aligned with a second portion ofthe radiation beam when the radiation beam is emitted by the radiationsource, each of the first and second portions of the selectivelytransmissive medium having a transmissivity that is changeable from afirst transmissivity to a second transmissivity different than the firsttransmissivity.
 48. The apparatus of claim 46 wherein the adaptivestructure includes a liquid crystal material having first and secondportions, each with a transmissivity that is changeable from a firsttransmissivity to a second transmissivity different than the firsttransmissivity.
 49. The apparatus of claim 46 wherein the adaptivestructure includes a reflective medium having a first portion alignedwith a first portion of the radiation beam when the radiation beam isemitted from the radiation source, the reflective medium having a secondportion aligned with a second portion of the radiation beam when theradiation beam is emitted by the radiation source, each of the first andsecond portions of the reflective medium being coupled to at least oneactuator to move from a first inclination angle relative to theradiation path to a second inclination angle relative to the radiationpath, the second inclination angle being different than the firstinclination.
 50. The apparatus of claim 46 wherein the adaptivestructure includes a reflective medium having a first portion alignedwith a first portion of the radiation beam when the radiation beam isemitted from the radiation source, the reflective medium having a secondportion aligned with a second portion of the radiation beam when theradiation beam is emitted by the radiation source, each of the first andsecond portions of the reflective medium being coupled to at least oneactuator to move from a first inclination angle relative to theradiation path to a second inclination angle relative to the radiationpath, the second inclination angle being different than the firstinclination angle, and wherein the apparatus further comprises: agrating positioned between the adaptive structure and the substratesupport, the grating having a first region with a first transmissivityand being optically aligned with the first portion of the reflectivemedium to receive at least part of the first portion of the radiationbeam when the first portion of the reflective medium has the firstinclination angle relative to the radiation path, the grating furtherhaving a second region with a second transmissivity greater than thefirst transmissivity and being optically aligned with the first portionof the reflective medium to receive at least part of the first portionof the radiation beam when the first portion of the reflective mediumhas the second inclination angle relative to the radiation path.
 51. Theapparatus of claim 46, further comprising a reticle positioned betweenthe adaptive structure and the substrate support, the reticle having atleast one reticle aperture positioned to pass the radiation toward thesubstrate support.
 52. The apparatus of claim 46, further comprising areticle having a reticle aperture positioned to pass radiation towardthe substrate support, the reticle being coupled to a reticle actuatorto move along a reticle path generally normal to the radiation pathproximate to the reticle, and wherein the support member is coupled to asupport member actuator to move along a support member path in adirection opposite the reticle and generally normal to the radiationpath while the reticle moves along the reticle path.
 53. The apparatusof claim 46, further comprising a reticle having a reticle aperturepositioned to pass radiation toward the substrate support, and whereinat least one of the support member and the reticle is coupled to atleast one actuator to sequentially align fields of the microlithographicsubstrate with the radiation beam when the microlithographic substrateis carried by the support member.
 54. An apparatus for irradiating amicrolithographic substrate, comprising: a substrate support having asupport surface positioned to carry a microlithographic substrate; aradiation source positioned to direct a radiation beam along a radiationpath toward the substrate support; a selectively transmissive mediumpositioned in the radiation path, the selectively transmissive mediumhaving a first portion aligned with a first portion of the radiationbeam when the radiation beam is emitted from the radiation source, theselectively transmissive medium having a second portion aligned with asecond portion of the radiation beam when the radiation beam is emittedby the radiation source, each of the first and second portions of theselectively transmissive medium having a transmissivity that ischangeable from a first transmissivity to a second transmissivitydifferent than the first transmissivity; and a controller operativelycoupled to the selectively transmissive medium to direct at least one ofthe first and second portions to change from the first transmissivity tothe second transmissivity.
 55. The apparatus of claim 46 wherein theselectively transmissive medium includes a liquid crystal material. 56.The apparatus of claim 46 wherein the first portion is configured tochange to the second transmissivity without becoming opaque.
 57. Theapparatus of claim 46 wherein the radiation source is configured to emita radiation beam having a wavelength of about 365 nanometers or less.58. The apparatus of claim 46, further comprising a reticle having areticle aperture positioned to pass radiation toward the substratesupport, the reticle being coupled to a reticle actuator to move along areticle path generally normal to the radiation path proximate to thereticle, and wherein the support member is coupled to a support memberactuator to move along a support member path in a direction opposite thereticle and generally normal to the radiation path while the reticlemoves along the reticle path.
 59. The apparatus of claim 46, furthercomprising a reticle having a reticle aperture positioned to passradiation toward the substrate support, and wherein at least one of thesupport member and the reticle is coupled to at least one actuator tosequentially align fields of the microlithographic substrate with theradiation beam when the microlithographic substrate is carried by thesupport member.
 60. An apparatus for irradiating a microlithographicsubstrate, comprising: a substrate support having a support surfacepositioned to carry a microlithographic substrate; a radiation sourcepositioned to direct a radiation beam along a radiation path toward thesubstrate support; a reflective medium positioned in the radiation path,the reflective medium having a first portion aligned with a firstportion of the radiation beam when the radiation beam is emitted fromthe radiation source, the reflective medium having a second portionaligned with a second portion of the radiation beam when the radiationbeam is emitted by the radiation source, each of the first and secondportions of the reflective medium being movable from a first inclinationangle relative to the radiation path to a second inclination anglerelative to the radiation path, the second inclination angle beingdifferent than the first inclination angle; a grating positioned betweenthe reflective medium and the substrate support, the grating having afirst region with a first transmissivity and being optically alignedwith the first portion of the reflective medium to receive the firstportion of the radiation beam when the first portion of the reflectivemedium has the first inclination angle relative to the radiation path,the grating further having a second region with a second transmissivitygreater than the first transmissivity and being optically aligned withat least part of the first portion of the reflective medium to receivethe first portion of the radiation beam when the first portion of thereflective medium has the second inclination angle relative to theradiation path; and a controller operatively coupled to the reflectivemedium to direct at least one of the first and second portions to changefrom the first inclination angle to the second inclination angle. 61.The apparatus of claim 60 wherein the grating has at least approximately90 percent open area.
 62. The apparatus of claim 60 wherein theradiation source is configured to emit a radiation beam having awavelength of about 365 nanometers or less.
 63. The apparatus of claim60, further comprising a reticle having a reticle aperture positioned topass radiation toward the substrate support, the reticle being coupledto a reticle actuator to move along a reticle path generally normal tothe radiation path proximate to the reticle, and wherein the supportmember is coupled to a support member actuator to move along a supportmember path in a direction opposite the reticle and generally normal tothe radiation path while the reticle moves along the reticle path. 64.The apparatus of claim 60, further comprising a reticle having a reticleaperture positioned to pass radiation toward the substrate support, andwherein at least one of the support member and the reticle is coupled toat least one actuator to sequentially align fields of themicrolithographic substrate with the radiation beam when themicrolithographic substrate is carried by the support member.
 65. Anapparatus for irradiating a microlithographic substrate, comprising: asubstrate support having a support surface positioned to carry amicrolithographic substrate; a radiation source positioned to direct aradiation beam along a radiation path toward the substrate support; areflective medium positioned in the radiation path and configured toreceive the radiation beam with a first intensity distribution andtransmit the radiation beam with a second intensity distributiondifferent than the first intensity distribution, the reflective mediumhaving a first portion aligned with a first portion of the radiationbeam when the radiation beam is emitted from the radiation source, thereflective medium having a second portion aligned with a second portionof the radiation beam when the radiation beam is emitted by theradiation source, each of the first and second portions of thereflective medium being movable from a first inclination angle relativeto the radiation path to a second inclination angle relative to theradiation path, the second inclination angle being different than thefirst inclination angle; a reticle positioned between the reflectivemedium and the substrate support to receive the radiation beam from thereflective medium, the reticle having at least one aperture positionedto project an image onto the microlithographic substrate when themicrolithographic substrate is carried by the substrate support; and acontroller operatively coupled to the reflective medium to direct atleast one of the first and second portions to change from the firstinclination angle to the second inclination angle.
 66. The apparatus ofclaim 65, further comprising a diffuser element positioned between thereflective medium and the reticle to smooth a distribution of radiationintensity of the radiation beam reflected from the reflective medium.67. The apparatus of claim 65 wherein the radiation source is configuredto emit a radiation beam having a wavelength of about 365 nanometers orless.
 68. The apparatus of claim 65 wherein the reticle is coupled to areticle actuator to move along a reticle path generally normal to theradiation path proximate to the reticle, and wherein the support memberis coupled to a support member actuator to move along a support memberpath in a direction opposite the reticle and generally normal to theradiation path while the reticle moves along the reticle path.
 69. Theapparatus of claim 65 wherein at least one of the support member and thereticle is coupled to at least one actuator to sequentially align fieldsof the microlithographic substrate with the radiation beam when themicrolithographic substrate is carried by the support member.